1. Field of the Invention
The present invention is generally concerned with squeegee heads of the type used in silkscreen printing machines, for example, for forcing the ink through the screen and for cleaning the screen.
2. Description of the prior art
A known squeegee head of this kind includes a squeegee carried by a squeegee-holder itself carried by a support. The squeegee is designed to be swept across the silk screen in one direction, pushing in front of it the ink to be forced through the screen, and is usually associated with a second squeegee which is swept in the opposite direction to clean the screen.
In practice the squeegee is applied to the screen at a particular angle in order to improve the sweeping action.
In addition to other factors including the mesh size of the screen, the so-called "contact free" distance between the screen and the object to be printed and the hardness of the squeegee, the angle at which the squeegee is applied to the screen is one parameter determining the thickness of the ink deposit on the object to be printed.
Good control of this thickness is essential in multi-color printing because the translucent colors are laid down in succession and the final color depends on the thickness of the ink deposit. To achieve good control of this thickness it is important to be able to vary the angle at which the squeegee is applied to the screen at will and to be able to adjust it accordingly.
In current squeegee heads the squeegee-holder is therefore mounted on its support so that its inclination can be adjusted by rotating it about a pivot axis parallel to the lengthwise direction of the squeegee.
At present, however, this pivot axis is at a relatively large distance from the free edge of the squeegee, the squeegee-holder being merely articulated to its support by a pivot.
Consequently, any modification of the squeegee angle modifies the height of the free edge of the squeegee and therefore the contact pressure with which the squeegee is applied to the screen.
If the contact pressure is too high, the printed object is over-inked and each dot printed on it spreads excessively, whereas if the contact pressure is too low there may be localized gaps in the printing.
Thus at present changing the squeegee angle requires modification of its height.
This complicates the adjustments required.
A general object of the present invention is an arrangement which can avoid this problem and confer other advantages.